1. Field of the Invention
This invention relates to a gage block and more particularly to a gage block for use with a sine bar to set up commonly used angles.
2. Description of the Related Art
Gage blocks are used with conventional sine bars to set up specific angles to be measured or a specific angle to be machined on a work piece.
Individual gage blocks are provided with two precision machined or ground parallel surfaces with a precisely controlled thickness. In use with a sine bar, the gage blocks are stacked up on the surface plate of the sine bar to produce the desired angle between the pivotable measuring plate and the surface plate.
Sine bars are commonly available in 3", 5" and 12" sizes which denotes the distance between the sine bar pivot point and the spherical ball which rests on the top surface of the stack of gage blocks. Since this distance is the hypotenuse of a right triangle with the combined height of the stacked gage blocks forming the side opposite the angle being set, the total height of the gage blocks must be equal to the product of the sine bar size and the sine of the angle being set. Thus for a 5" sine bar, the combined height of the stacked gage blocks for a 10.degree. angle must be 5 sine 10.degree. or 5.times.0.17365=0.8682".
Gage blocks are supplied in sets of over 80 blocks to provide desired angles up to 45.degree., as is well known in the art. A minimum of two to four blocks are usually necessary to set a desired angle. Using a 5" sine bar to set up common 5.degree. angle increments, a 5.degree. angle can be set using three gage blocks with thicknesses of 0.1008", 0.1350" and 0.2000". A minimum number of blocks for 15.degree. would be four blocks having thicknesses of 0.1001", 0.1440", 0.0500" and 1.0000, and a minimum number of blocks for 45.degree. would be four blocks having thicknesses of 0.1005", 0.1350", 0.3000" and 3.0000. Sixteen blocks would be required in different combinations to set up the common angles of 5.degree., 10.degree., 15.degree., 20.degree., 30.degree. and 45.degree..
Moreover, the user must have a sine table and must multiply the sine of the angle required by 5 to select the proper combination for the angle. For example, for 15.degree., the sine is 0.25882" requiring a total height of blocks of 1.2941". Mistakes in the selection of the blocks to provide a given total height can be easily made so that extreme care must be used in setting individual angles
While there have been innovations in sine bar constructions throughout the years, primarily to allow incremental angle settings by the use a vernier scale or the like, such as those shown in U.S. Pat. Nos. 1,366,396 and 4,389,785, they still require the selection of individual gage block combinations to produce the individual desired angle.